Study On Electrolytic Preparation Of Copper Powder In Choline Chloride-urea Deep Eutectic Solvent

Copper powder has excellent electrical conductivity,thermal conductivity,catalytic activity and other excellent properties,widely used in conductive paste,solid fuel cells and chemical catalysts and other fields.The present research shows that acidic sulfate system is usually used in electrolytic preparation of copper powder,which has some problems such as low current efficiency,uneven particle size of copper powder and so on.Moreover,copper powder is easy to oxidize,so it needs coating and other follow-up treatment.Therefore,it is of great significance to find an efficient and green electrolyte to replace the aqueous electrolyte.Deep eutectic solvent（DES）is a good alternative electrolyte,which has the advantages of high ionic conductivity,wide electrochemical window and good electrochemical stability.In this paper,choline chloride-urea deep eutectic solvent added with CuCl was used as electrolyte.The dissolution behavior of copper anode in deep eutectic solvent electrolyte and the electrochemical deposition behavior of copper ion in this electrolyte were studied.It is found that in this electrolyte,the presence of copper ions is mainly Cu（I）ions,which can significantly reduce the energy consumption compared with the conventional aqueous solution electrolyte,and the copper powder has good oxidation resistance.Therefore,the preparation of copper powder in this electrolyte has a good application prospect.details as follows:（1）The dissolution behavior of copper anode in Ch Cl-Urea-CuCl DES electrolyte was studied by electrochemical test.It was found that copper anode dissolved mainly in the form of Cu（I）ion in this electrolyte.The existence of Cu（I）ion is in the form of[CuCl₂]^-and[CuCl₃]^2-complex.The anodic dissolution process of copper is controlled by diffusion.A model of surface passivation of copper anode during dissolution is also established.In addition,it is shown for the first time that pure copper can be polished in Ch Cl-Urea DES.（2）The effect of experimental conditions on the ratio of Cu（I）ion concentration to total copper ion concentration was investigated.The results show that Cu（I）ions account for the highest proportion of 93.18%in the electrolyte with a cathode current density of 10m A·cm^-2,a temperature of 353K and a CuCl concentration of50mmol·L^-1.In addition,the diffusion coefficient of Cu（I）ions in Ch Cl-Urea DES increases with the increase of temperature,and increases first and then decreases with the increase of CuCl concentration.This is because the conductivity of the electrolyte increases with increasing temperature,but increases first and then decreases with increasing CuCl concentration.（3）The effects of various experimental conditions on the deposition of copper on the titanium matrix were investigated.The experimental factors such as cathode current density,CuCl concentration,electrolysis temperature and electrolysis time have a great influence on the morphology and grain size of copper deposited on the titanium substrate.Among them,when the cathode current density is 10 m A·cm^-2,the CuCl concentration is 50 mmol·L^-1,the electrolysis temperature is 353K,and the electrolysis time is 5h,the current efficiency and DC power consumption of the copper powder prepared on the titanium sheet are optimal,respectively.97.25%and345.64 KW·h·t^-1.（4）Electrochemical measurements were used to study the deposition mechanism of copper on different cathode substrates.It was found that the temperature and CuCl concentration had a great effect on the cathodic polarization of copper on titanium substrate.Moreover,the reduction nucleation of copper ions on titanium substrate does not belong to the three-dimensional nucleation model.The variation of cathodic polarization degree of copper on stainless steel substrate is similar to that on titanium substrate,but the reduction nucleation mode of copper on stainless steel substrate is three-dimensional instantaneous nucleation.In addition,it is found that different deposition potential and different CuCl concentration have great influence on the morphology of copper deposition on stainless steel substrate.